In the past years, there has been extended efforts in the development of high capacitance electrochemical energy storage devices, especially capacitors and batteries, for use in reduced volumetric areas. Both capacitors and batteries store energy by the separation of positive and negative charges. The need to store greater amounts of energy in a smaller package continues to drive new research.
Barium titanate (BaTiO.sub.3) has been studied for use in such microelectronic applications. Such studies have included the different forms of barium titanate including powder, bulk, thin film and multilayer owing to their excellent electronic and optical characteristics including high dielectric constant, transparency in visible wavelength, and high non-linear optical susceptibility.
The use of barium titanates in electric vehicles is further highly desired. Presently, automotive internal combustion engines are increasingly being challenged by environmental concerns, favoring an increased role for electric vehicles. Thus, supercapacitors, as well as batteries, play a major role in this developing market.
Supercapacitors having capacitances in the range of milli-Farads to Farads have suffered from slow charging and discharging cycles in light of their high series resistance (i.e., large RC time constants). In addition, they often rely on corrosive and environmentally unfriendly electrolytes. For instance, the BaTiO.sub.3 thin films set forth in T. Hayashi, Jpn. J. Appl. Phys., 32 4092 (1993) have a capacitance unacceptable for use in electric vehicles as well as other industries. Alternative nanosized capacitors are constantly being sought.
Need exists therefore for an electrical energy storage device that combines the desirable features of conventional capacitors yet can store much larger amounts of energy in a smaller package and can be manufactured at reasonable costs.